DVD Decrypter Problem/Question?

I am new to this site but not too new to the Backing up process. One quick question I have is: Why is it wheni back up one of my movies with DVD Shrink everything is perfect and when I use DVD Decrypter it doubles the size of the file and forces me to burn to a Dual Layer DVD? And yes I have tried this with te same DVD.

???

DVD Shrink shrinks a movie to fit on a blank DVD-R, DVD Decrypter rips a DVD, thus keeping the original size which in almost all cases is quite larger than 4,5 GB.